1. Field of the Invention
The present invention relates to a protection circuit assembly and a battery pack having the same.
2. Description of the Related Art
Secondary batteries are rechargeable and can be repeatedly used. Thus, secondary batteries may be more economical than disposable batteries.
Also, secondary batteries can have a high capacity with a small volume, allowing secondary batteries to be used in high power products such as hybrid cars and electric tools as well as handheld electrical appliances.
Secondary batteries include, for example, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries and lithium secondary batteries.
Lithium secondary batteries are widely used because they are compact and have high capacity, a high operating voltage and a high energy density per unit weight.
Lithium secondary batteries may be formed by accommodating an electrode assembly and an electrolyte in a case, and sealing the case.
The electrode assembly may be formed in a jelly-roll shape by stacking and winding a positive electrode plate, a negative electrode plate and a separator.
Lithium secondary batteries may be classified into a can type and a pouch type depending on the shape of the case, and the can-type batteries may be classified into a rectangular type and a cylindrical type.
A lithium secondary battery may be electrically connected to a protection circuit board to prevent hazards caused by abnormal operation such as overcharge, overdischarge and overcurrent.
The protection circuit board may include protection devices such as a PTC thermistor, a protection circuit, a fuse and a temperature sensor.
The secondary battery and the protection circuit board may be used in the shape of a battery pack, which may be a hard pack type in which the secondary battery and the protection circuit board are accommodated in a separate case.
Further, the battery pack may be an inner pack type in which the protection circuit board is covered with a cover to be protected and an exterior is tubed and labeled.
In that case, the protection circuit board may include a lead plate to be electrically connected with the secondary battery.
Since the protection circuit board may include a connection terminal in contact with a lead plate, a space for mounting the protection devices is reduced.
In addition, a part of the lead plate may be exposed to facilitate welding, such that the lead plate can be attached to the secondary battery by laser welding.
Conventionally, the protection circuit board may be relatively small and it may be difficult to partially expose the lead plates in contact with both ends of the protection circuit board.
Thus, a space for mounting protection devices becomes smaller as the protection circuit board becomes smaller, making exposure of the lead plates more difficult.